Catalytic hydrogenation of recycle solvent in a 150t/d pilot plant of the NEDOL coal liquefaction process

Effect of reaction temperature on hydrotreatment of a recycle solvent in the NEDOL coal liquefaction process was studied from the data obtained by the operation of a 150 t/d pilot plant. Hydrotreatment of the recycle solvent was carried out under a hydrogen pressure of 100 kg/cm2 G over Ni–Mo/Al2O3 catalyst in a fixed bed reactor. As the reaction temperature increased from 290 to 330°C, the hydrogen gas consumption increased from 0.4 to 1.0 wt%. About 50% of consumed hydrogen was utilized for the hydrogenation of aromatic rings in the recycle solvent, and the rest for the removal of nitrogen and oxygen from the recycle solvent, and for cracking of the recycle solvent. Among aromatic compounds contained in the recycle solvent, two-ring aromatics and hydroaromatics and their derivatives (aromatics of naphthalene type) shared the largest fraction. The aromatics of the naphthalene type underwent hydrogenation faster than those of the phenanthrene type, the anthracene type, and the pyrene type. Under the reaction conditions examined, excess hydrogenation of the aromatics of the naphthalene type to form perhydrogenated compounds (naphthenes) did not take place so extensively; i.e. tetrahydronaphthalenes formed much more than decahydronaphthalenes.